Why Do My Energy Efficient Windows Get Misty In The Mornings?

We’ve all at some point pulled back our curtains at home first thing in the morning and been greeted by the sight of condensation on our windows.

If you don’t know the first thing about condensation and have often wondered why this mistiness clouds your windows at times, allow us to firstly give you some important background on condensation.

Condensation is “the act or process of changing from a gas to a liquid or solid state”.

It arises when the temperature of an object (in this case, the glass) falls below the ‘Dew Point’ or atmospheric temperature (determined by the water in the atmosphere and air temperature), causing water vapour in the air to condense and water droplets to form.

In humid conditions, condensation most often emerges in high temperatures, but it can also form during cold spells when humidity is low. It’s the difference between internal and external temperatures, and the glass, that primarily causes condensation on windows.

You shouldn’t be alarmed about condensation forming on the external side of your windows though if your windows are recently new and thermally efficient – they’re not faulty!

It can be put down to the differing temperatures between outdoor air and the external glass pane. When the two of them collide, it causes external condensation, but not on all windows. If the windows of your neighbours don’t have external condensation, it just means that their windows aren’t as thermally efficient as your own.

You never quite know when condensation might strike as it depends on a series of environmental and geographical factors. However, external condensation is most likely between March and October when the Dew Point is at its highest and temperatures fluctuate strongly either side of sunrise or when warm air currents are replaced by cool fronts.

A little bit of exposure to sunlight or a slight breeze usually helps condensation to evaporate.

If you want to know more about condensation and how it comes about, visit our Helpful Guides page and download a FREE copy of our document dedicated to the subject.